Radio sources in the Chandra Galactic Bulge survey

TL;DR

This paper identifies and classifies radio sources in the Chandra Galactic Bulge survey, primarily finding background AGN and exploring their properties using multi-wavelength data.

Contribution

It introduces a classification scheme for radio/X-ray sources in the Galactic Plane and applies it to identify the nature of sources in the survey region.

Findings

Most sources are background AGN confirmed by multi-wavelength data.

One source may be a radio pulsar, another a planetary nebula.

None are likely due to stellar coronal activity.

Abstract

We discuss radio sources in the Chandra Galactic Bulge survey region. By cross-matching the X-ray sources in this field with the NVSS archival data, we find 12 candidate matches. We present a classification scheme for radio/X-ray matches in surveys taken in or near the Galactic Plane, taking into account other multi-wavelength data. We show that none of the matches found here is likely to be due to coronal activity from normal stars because the radio to X-ray flux ratios are systematically too high. We show that one of the sources could be a radio pulsar, and that one could be a planetary nebula, but that the bulk of the sources are likely to be background active galactic nuclei (AGN), with many confirmed through a variety of approaches. Several of the AGN are bright enough in the near infrared (and presumably in the optical) to use as probes of the interstellar medium in the inner Galaxy.